By Paul Thompson
VOICE ONE:
This is Steve Ember.
VOICE TWO:
And this is Phoebe Zimmermann with the VOA Special English
program, EXPLORATIONS. Today we tell about a device you can hold in
your hand. It permits you to find your way across mountains, through
deserts and across oceans without ever getting lost.
VOICE ONE:
Let us begin back on June
twenty-seventh, Eighteen-Fifty-One. We are on the sailing ship,
"Flying Cloud," in the Atlantic Ocean. The Flying Cloud is under the
command of Captain Josiah Cressy.
For many days now, Captain Cressy has made the huge ship travel
at speeds that were not thought possible. The crew is frightened by
the speed. No ship in history has ever traveled this fast. The crew
also is frightened because the ship is sailing in some of the most
dangerous waters in the world.
The Flying Cloud is near Cape Horn at the end of the South
American continent. The weather has been bad for several days. The
person responsible for guiding the ship must be able to see the Sun
or a star to know the position of the ship. The stormy weather has
prevented this for several days.
VOICE TWO:
The person who plans the
directions for a sailing trip is usually the ship's captain. On the
Flying Cloud, however, the captain's wife does this job.
Her name is Eleanor Cressy. She is famous as an expert navigator.
She has planned this trip through the dangerous waters near Cape
Horn. Many underwater rocks are found here. To guide the ship
safely, she must know where the ship is at all times.
Eleanor Cressy must use a method called "Dead Reckoning" because
she has not been able to see the Sun or stars to find the ship's
true position. Dead Reckoning is extremely difficult. It is part
science, and part estimate.
To find the position of the Flying Cloud, Missus Cressy must use
the last known position of the ship. She also has to consider the
ship's direction, its speed and the movement of waves or the ocean
current.
Here, near Cape Horn, she is permitted no mistakes. Many ships
have sunk in this part of the world. Hour after hour, Eleanor Cressy
uses mathematics to find the ship's Dead Reckoning position. She
does this again and again, carefully searching for mistakes. The
lives of the crew and the future of the ship are her responsibility.
VOICE ONE:
Eleanor Cressy demonstrates her great skill at navigation the
next day. On the morning of June twenty-ninth, Captain Cressy can
see Cape Horn, just eight kilometers to the north. The ship is
exactly where Eleanor said it should be. It is safe and will
continue on to San Francisco, California, faster than any sailing
ship ever.
VOICE TWO:
Eleanor Cressy's job in Eighteen-Fifty-One was important and
extremely difficult. The job of navigator did not change much until
the middle of the Twentieth Century. At sea or on land, finding the
correct direction to travel has always been a problem.
However, within the past several years, the problem of navigation
has greatly changed. Dead Reckoning navigation is a thing of the
ancient past. Now, people do not need the skills of Eleanor Cressy
to navigate. They can use a simple device that will permit them to
navigate anywhere in the world. It uses a technology called "Global
Positioning System," or G-P-S.
VOICE ONE:
G-P-S is able to show your exact
position on Earth. Weather does not affect the device. Many G-P-S
devices can be held in the hand. Some are larger, and meant to be
placed in ships, automobiles, trucks, airplanes or other aircraft.
Whatever the size, the device works much the same way. The G-P-S
device is a radio receiver. It receives information from twenty-four
satellites in orbit around the Earth. The satellites are placed so
that a G-P-S device on the surface of the Earth can receive
information from at least four of the satellites at any time.
VOICE TWO:
A satellite sends information, including the exact time at which
it is operating. It also sends information about the position of
other satellites.
This information travels from the satellite to the G-P-S device
at almost the speed of light. But the satellite is far enough away
to permit the device to measure the distance.
The G-P-S device uses the time the information was sent to find
its distance from the satellite. The device measures the exact
distance to four satellites to establish its position on Earth. The
G-P-S device can do this second by second, minute by minute, day
after day and arrive an the correct answer all the time.
You can place the device in a ship, a car or other moving
vehicle. Then you can watch the position information change as the
vehicle moves. In fact, the G-P-S device will give both your
direction and the speed you are traveling.
VOICE ONE:
The United States government owns the twenty-four satellites that
provide the information for G-P-S. The Department of Defense
controls the satellites.
The first G-P-S satellite system was called NAVSTAR. It was
launched in February, Nineteen-Seventy-Eight. The NAVSTAR satellites
were created to provide extremely correct navigation information to
American military ships and aircraft.
A few years later, President Ronald Reagan signed a document that
permitted information from NAVSTAR to be used by anyone. He did this
after a Korean Air Lines flight was lost. The Korean airplane had
flown by mistake into airspace over the Soviet Union in
nineteen-eighty-three. It was shot down by Soviet military aircraft.
President Reagan said the American satellite navigation system would
help prevent such accidents in the future.
It costs nothing to use the satellite information. All you need
is a G-P-S device to receive the information.
The least costly G-P-S devices sell for about one-hundred
dollars. The smallest devices can be held in the hand. Devices for
aircraft or ships are larger. They may cost several thousands of
dollars.
VOICE TWO:
After President Reagan permitted the public use of American
navigation information, several electronics companies began making
the G-P-S devices. However, there was a problem. The Defense
Department would not let the satellites send the exact information
to the public. Defense officials made sure the satellites sent
information with mistakes. This was done so the information could
not be used by military forces of any future enemy.
In May of two-thousand, the United States announced that such a
security measure was no longer needed. The government turned off the
equipment preventing satellites from providing the correct
information.
Today, a G-P-S device that receives information from four
satellites at the same time will show your correct position on Earth
to within ten meters. It can also tell you the speed of your
vehicle, the direction you are traveling, how far you have traveled,
and the distance remaining until the end of your trip.
VOICE ONE:
G-P-S devices are popular in the United States. Many companies
make and sell them. Most of the devices come with a receiver that
looks like a small television. The less costly G-P-S devices provide
information in black and white. More costly ones provide the
information in color.
Many G-P-S devices can be linked to computers. The computers
place information into the device including maps of city streets and
major roads between cities.
The user of the device enters information using the controls. The
G-P-S provides information about the direction of travel and tells
how to get where you want to go. The device will correctly guide you
from road to road and street to street, warning before a left and
right turn must be made. The device also remembers where it has
been. So it can guide the G-P-S user home again.
Recently, some companies started producing G-P-S devices that
speak the directions. A person driving a vehicle does not have to
look at the device for information. A person only has to listen.
Here is an example. This G-P-S device is from the Garmin Company.
Listen as the voice gives directions.
VOICE TWO:
As you can see, the new G-P-S devices can help anyone get to
where they want to go. And, they can do this just as well as the
famous Eleanor Cressy did one-hundred-fifty years ago.
VOICE ONE:
This VOA Special English program was written by Paul Thompson and
produced by Caty Weaver. This is Steve Ember.
VOICE TWO:
And this is Phoebe Zimmermann. Join us again next week for
another EXPLORATIONS program on the Voice of America.
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VOA Special English
1.6万-1.7万下载 / 0人喜欢 / 6人评论
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一款学习英语的小应用。
VOA Special English
一款学习英语的小应用。功能强大的练习VOA听力的软件。
－ 离线下载Voice of America (VOA)的文章和音频MP3
－ 有收藏功能
优化了下载性能
- 对应OA网站的再次改版
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Ver3.0- 全新的操作体验，更佳顺畅的使用
怎么用不了么？
正确主义蒸珍妮
andytianlu
我觉得相当不错，学习好帮手
我下了 怎么用不了呢
我觉得挺好用的，是我想要的。用智器ten2听voa慢速英语，很好
亲，想发表评论请下载哦～
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